Electrocardiogram measurement apparatus

ABSTRACT

The electrocardiogram measurement apparatus includes: two amplifiers for receiving electrocardiogram signals from a first electrode and a second electrode; one electrode driving unit; a third electrode for receiving an output of the electrode driving unit; an A/D converter connected to an output terminal of each of the two amplifiers and converting analog signals into digital signals; a microcontroller for receiving the digital signals from the A/D converter; and a communication means for transmitting the digital signal, wherein: the microcontroller is supplied with power from a battery; the microcontroller controls the A/D converter and the communication means; and each of the two amplifiers amplifies one electrocardiogram signal so as to simultaneously measure two electrocardiogram signals.

CROSS REFERENCE

This is a continuation of application Ser. No. 16/768,769 which is nowpending.

BACKGROUND

An electrocardiography system provides a waveform of an electricalsignal, namely, an electrocardiogram, which contains very useful buteasily obtainable information to analyze the condition of a patient'sheart. It can be said that the electrocardiography system includes anelectrocardiogram measurement apparatus (a measurement sensor) and acomputer. In these days, almost all individuals use a smartphone. Asmartphone can be considered a computer capable of wirelesscommunication and providing a good display. Therefore, the combinationof the electrocardiogram measurement apparatus (measurement sensor) andthe smartphone can be a good electrocardiography system. The presentinvention relates to an electrocardiogram measurement apparatus(measurement sensor) that an individual can use in association with asmartphone. According to International Patent Classification (IPC), theapparatus for measuring an electrocardiogram according to the presentinvention is classified into class A61B 5/04 to which detecting,measuring or recording bioelectric signals of the body or parts thereofbelongs.

An electrocardiography system is a useful apparatus capable ofconveniently diagnosing a patient's heart condition. Electrocardiographysystems can be classified into several types depending on the purposethereof. The standard of hospital electrocardiography systems which areused to obtain as much information as possible is a 12-channelelectrocardiography system employing 10 wet electrodes. A patientmonitoring system is used to continuously measure a patient's heartcondition with a small number of wet electrodes attached to thepatient's body. A Holter recorder and an event recorder that a user canuse by themselves while moving around have the following essentialfeatures. These features include a compact size, battery-poweredoperation, a storage device provided to store measured data, and acommunication device capable of transmitting the data. The Holterrecorder usually uses 4 to 6 wet electrodes and cables connected to theelectrodes, and provides a multi-channel ECG. However, the user feelsuncomfortable about the Holter recorder because the wet electrodesconnected to the cables are attached to the body. Recently releasedelectrocardiography systems such as a patch type system also requireelectrodes to be kept attached to the body.

The event recorder allows users to carry the recorder and measure ECG ontheir own when they feel an abnormality in their heart. Therefore, theevent recorder is compact and does not have a cable for connectingelectrodes, and dry electrodes are provided on the surface of the eventrecorder. The conventional event recorder is a 1-channelelectrocardiography system, i.e., a 1-lead electrocardiography systemthat measures one ECG signal while both hands of a user are in contactwith two electrodes.

An electrocardiogram measurement apparatus which is sought or requiredby the present invention is required to be convenient for personal use,to provide accurate and abundant electrocardiogram measurements, and tobe compact so as to be easily carried. The required apparatus forconvenient personal use should be able to transmit data via wirelesscommunication to a smartphone. To this end, the required apparatusshould be battery-powered. To increase battery life while obtaining acompact size of the apparatus, the required apparatus should not includea display, and the electrocardiogram should be displayed on asmartphone.

In the present invention, in order to provide accurate and abundant ECGmeasurements, two limb leads are directly measured at the same time. Asdescribed later, in the present invention, four leads can be calculatedand provided based on the two limb lead measurements performedsimultaneously. Conventionally, regarding an electrocardiogram,“channel” and “lead” are used interchangeably to mean one ECG signal orECG voltage. Regarding an electrocardiogram, the word “simultaneously”should be used very carefully. The phrase “simultaneously” means thatoperations are not “sequential”. In other words, measuring two leadssimultaneously should literally mean measuring two ECG voltagessubstantially at one moment. Specifically, when lead II is sampled whilethe voltage of lead I is sampled with a constant sampling period,measurements can be said to be performed simultaneously only if samplinglead II is performed within a shorter time than the sampling period fromeach time of sampling Lead I. The word “measurement” should also be usedcarefully. The word “measurement” should be mentioned only when aphysical quantity is actually measured. In digital measurement, onemeasurement should mean one AD conversion. As will be described later,for example, by measuring lead I and lead III in electrocardiogrammeasurement, lead II can be calculated according to Kirchhoff's voltagelaw. In this case, lead II must be expressed as “calculated,” not“measured,” which can cause confusion.

One of the most difficult challenges in electrocardiogram measurement isto remove power line interference included in the electrocardiogramsignal. A well-known method for removing power line interference isDriven Right Leg (DRL). Substantially, almost all electrocardiogramsremove power line interference by the DRL. A drawback of the DRL is thatone DRL electrode should be attached to the right leg or a lower rightpart of a torso. Therefore, in order to measure two limb leads using theDRL technique, conventional technology requires four electrodesincluding the DRL electrode to be brought into contact with the body.However, an important issue raised at this time is that a cable must beused or the size of the apparatus is increased because the DRL electrodeshould be brought into contact with the lower right abdomen. In otherwords, it is difficult to scale down an electrocardiogram measurementapparatus configured to measure two leads using a DRL electrode to thesize of a credit card. Another important issue is that if the DRLelectrode is arranged adjacent to another electrode and brought intocontact with the human body, the voltage of the adjacent electrode isdistorted because the voltage of the DRL electrode includes componentsof an electrocardiogram signal. Removing power line interference withoutusing the DRL electrode is very difficult and requires use of a specialcircuit (In-Duk Hwang and John G. Webster, Direct InterferenceCancelling for Two-Electrode Biopotential Amplifier, IEEE Transaction onBiomedical Engineering, Vol. 55, No. 11, pp. 2620-2627, 2008). In orderto remove the power line interference, multiple filters having asignificantly high quality factor (Q) may be required, and manufacturingand calibration of the multiple filters may be difficult.

The electrode impedance of a dry electrode is large, and accordingly thedry electrode generates greater power line interference. However, in theelectrocardiogram measurement, for user convenience, it is necessary touse a dry electrode attached to the case surface of an electrocardiogrammeasurement apparatus without using a wet electrode connected to acable. In addition, it is necessary to reduce the number of dryelectrodes for user convenience. It is also required not to bring theDRL electrode into contact with the right leg or a lower right part of atorso. However, in the conventional technology, it is difficult toprovide an electrocardiogram measurement apparatus that removes powerline interference with a minimum number of electrodes and does not use acable.

In order to solve the above problems and necessities, the presentinvention uses dry electrodes and does not use a cable for userconvenience. To measure two limb leads simultaneously, the presentinvention uses two amplifiers, one electrode driver, and threeelectrodes connected thereto. The electrocardiogram apparatus accordingto the present invention provides a plate-shaped electrocardiogramapparatus having two dry electrodes separated from each other on onesurface and one dry electrode on the other surface for user convenience.In addition, the present invention provides a method for removing powerline interference in order not to use a DRL electrode.

As will be described later, the present invention discloses anelectrocardiogram measurement apparatus including three electrodes,wherein the power line interference current flows concentrated throughone electrode connected to the electrode driver, and two amplifiersconnected to the other two electrodes among the three electrodes eachamplify one electrocardiogram signal to measure two electrocardiogramsignals simultaneously. Here, one amplifier serves to amplify onesignal. In an actual configuration, one amplifier may represent a setcomposed of multiple cascaded amplification stages or active filters.

As described below, the conventional technology has failed to provide atechnical solution provided by the present invention.

Righter (U.S. Pat. No. 5,191,891, 1993) discloses a watch-type deviceequipped with three electrodes. This device obtains only one ECG signal.

Amluck (DE 201 19965, 2002) discloses an electrocardiogram apparatusprovided with two electrodes on the top and one electrode on the bottom.This apparatus measures only one lead. In addition, unlike the presentinvention, Amluck has a display and input/output buttons.

Wei et al. (U.S. Pat. No. 6,721,591, 2004) discloses that six electrodesincluding the ground electrode and RL electrode are used. Wei et al.discloses a method of measuring 4 leads and calculating the remaining 8leads.

Kazuhiro (JP2007195690, 2007) discloses an apparatus equipped with adisplay and four electrodes including a ground electrode.

Tso (US Pub. No. 2008/0114221, 2008) discloses a meter including threeelectrodes. However, according to Tso, two electrodes are touchedsimultaneously with one hand to measure one limb lead, for example, leadI. Since one lead is measured at a time in this way, three measurementsneed to be performed sequentially to obtain three limb leads. Inaddition, according to Tso, even an augmented limb lead, which does notneed to be measured directly, is directly measured and a separateplatform is used for this measurement.

Chan et al. (US Pub. No. 2010/0076331, 2010) disclose a watch includingthree electrodes. However, according to Cho et al., three leads aremeasured using three differential amplifiers. In addition, Chan et al.uses three filters connected to each of the amplifiers to reduce thenoise in a signal.

Bojovic et al. (U.S. Pat. No. 7,647,093, 2010) discloses a method forcalculating 12 lead signals by measuring three special (non-standard)leads. However, to measure three leads, consisting of one limb lead(lead I) and two special (non-standard) leads obtained from a chest,five electrodes including one ground electrode, on both sides of aplate-shaped apparatus, and three amplifiers are provided.

Saldivar (US Pub. No. 2011/0306859, 2011) discloses a cellular phonecradle. Saldivar discloses that three electrodes are provided on oneside of the cradle. However, Saldivar uses a lead selector and onedifferential amplifier 68 connected to two of the three electrodes tomeasure one lead sequentially (see FIG. 4C and paragraph [0054]). Thatis, according to Saldivar, 3 leads are measured sequentially one at atime.

Berkner et al. (U.S. Pat. No. 8,903,477, 2014) relates to a method ofcalculating 12 lead signals through sequential measurements carried outby sequentially moving an apparatus using 3 or 4 electrodes disposed onboth sides of a housing. However, Berkner et al. does not disclose thedetailed structure and shape of the apparatus, including how eachelectrode is connected internally. Most importantly, Berkner employs oneamplifier 316 and one filter module 304. When one amplifier 316 and onefilter module 304 are used, for example, measuring two leads requirestwo measurements to be performed sequentially. Specifically, Berknerdiscloses “ . . . so in a system comprising only 3 electrodes, thereference electrode is different and shifts for each lead measurement.This may be done by designated software and/or hardware optionallycomprising a switch.” The above technique indicates that Berkner usesone amplifier 316 and one filter 304 to measure one lead at a time andperforms multiple measurements sequentially. That is, the method ofBerkner et al. has many disadvantages compared to the method ofmeasuring two leads simultaneously using three electrodes and twoamplifiers as presented in the present invention.

Amital (US Pub. No. 2014/0163349, 2014) discloses that a common modecancellation signal is generated from three electrodes in an apparatusprovided with four electrodes and a common mode signal is removed bycoupling the common mode cancellation signal to the other electrode (seeclaim 1). This technique is a traditional DRL method well known beforeAmital.

Thomson et al. (US Pub. No. 2015/0018660, 2015) disclose a smartphonecase with three electrodes attached. The smartphone case of Thomson hasa hole in the front such that the smartphone screen can be seen.However, it fails to present a method for measuring two leadssimultaneously using two amplifiers. In addition, since the apparatus ofThomson uses ultrasonic communication, a communication-related issue canbe raised if the smartphone and the apparatus are separated by even aslight distance (about 1 foot). Further, if the user changes one'ssmartphone the user may not be allowed to use the existing Thomson'ssmartphone case.

Drake (US Pub. No. 2016/0135701, 2016) discloses that three electrodesare provided on one side of a mobile device to provide 6 leads. However,Drake discloses “comprises one or more amplifiers configured to amplifyanalog signals received from the three electrodes” (see paragraph [0025]and claim 4). Therefore, Drake is not clear about a key part of theinvention: how many amplifiers are used and how the amplifiers areconnected to the three electrodes. Further, Drake discloses “The ECGdevice 102 can include a signal processor 116, which can be configuredto perform one or more signal processing operations on the signalsreceived from the right arm electrode 108, from the left arm electrode110, and from the left leg electrode 112” (see paragraph).

Therefore, Drake receives three signals. Also, Drake is not clear aboutwhether three signals are received simultaneously or sequentially. Drakealso discloses “Various embodiments disclosed herein can relate to ahandheld electrocardiographic device for simultaneous acquisition of sixleads.” (see paragraph [0019]), where Drake uses the word “simultaneous”incorrectly, inappropriately and indefinitely. The structure of thedevice of Drake can be considered to be similar to that of the device ofThomson. In Drake, three electrodes are disposed on one side of theapparatus. Therefore, as with Thomson et al., it is difficult to bringthree electrodes into contact with both hands and the bodysimultaneously.

The device of Saldivar (WO 2017/066040, 2017) uses a lead selectionstage 250 to connect three electrodes to one amplifier 210. In addition,the device of Saldivar performs six measurements sequentially to obtainsix leads. In other words, the device of Saldivar does not measuremultiple leads simultaneously. The device of Saldivar also directlymeasures three augmented limb leads sequentially.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the aboveproblems, and it is an object of the present invention to provide anelectrocardiogram apparatus having three electrodes and two amplifiersassociated with two limb leads to measure the two limb leadssimultaneously with one electrocardiogram apparatus. It is medicallyvery important to measure two limb leads simultaneously. This is becauseit is more time consuming and inconvenient to measure two leadssequentially. More importantly, two limb leads measured at differenttimes may not correlate with each other and may cause confusion indetailed arrhythmia discrimination. The electrocardiogram apparatusaccording to the present invention includes a plate-shapedelectrocardiogram apparatus having two dry electrodes separated fromeach other on one surface and one dry electrode disposed on the othersurface for user convenience. It is another object of the presentinvention to provide a method for removing power line interference inorder not to use a DRL electrode. It is an object of the presentinvention to disclose a convenient electrocardiogram measurement methodbringing two electrodes into contact with two hands and one electrodeinto the body and an electrocardiogram measurement apparatus having astructure proper thereto.

The appearance, operation principle, configuration, and usage of theelectrocardiogram apparatus according to the present invention forsolving the above problems are as follows. The present invention solvesthe above problems through systematic and analytical circuit design andsoftware production.

In accordance with one aspect of the present invention, provided is anelectrocardiogram measurement apparatus comprising:

a first electrode and a second electrode configured to receive twoelectrocardiogram voltages of a body part in contact therewith,respectively;

two amplifiers configured to receive the two electrocardiogram voltagesfrom the first electrode and the second electrode, respectively;

one electrode driver configured to output a driving voltage;

a third electrode configured to receive the output of the electrodedriver and transmit the output of the electrode driver to the body partin contact therewith;

an AD converter connected to an output terminal of each of the twoamplifiers to convert output signals of the two amplifiers into twodigital signals;

a microcontroller configured to receive the two digital signals of theAD converter; and

a communication means configured to transmit the two digital signals.

The microcontroller is supplied with battery power.

The microcontroller controls the AD converter and the communicationmeans.

The two amplifiers each receive and amplify one electrocardiogramvoltage simultaneously, and an output impedance of the electrode driveris less than an input impedance of each of the two amplifiers.

FIG. 1 shows an electrocardiogram measurement apparatus 100 according tothe present invention. The electrocardiogram measurement apparatus 100includes three electrodes 111, 112, and 113 on the surface thereof. Twoelectrodes 111 and 112 spaced apart from each other by a predetermineddistance are installed on one surface of the electrocardiogrammeasurement apparatus 100, and one electrode 113 is installed on theother surface.

FIG. 2 illustrates a method for a user to measure an electrocardiogramin a 6-channel mode using the electrocardiogram measurement apparatus100 according to the present invention. The user makes contact with theelectrodes 111 and 112 provided on one surface of the electrocardiogrammeasurement apparatus 100 with both hands, and brings the electrode 113provided on the other surface into contact with the left lower abdomen(or left leg) of the user. When the three electrodes are brought intocontact with the user's body in this way, two limb leads can bemeasured, and four leads can be additionally calculated and obtained asdescribed below. The measurement method of FIG. 2 is provided by thepresent invention to obtain a 6-channel electrocardiogram mostconveniently. In addition, the present invention provides an apparatusmost suitable for the measurement method of FIG. 2 . The principle ofthe measurement method is as follows.

A traditional 12-lead ECG is disclosed in, for example, [ANSI/AAMI/IEC60601-2-25:2011, Medical electrical equipment-part 2-25: Particularrequirements for the basic safety and essential performance ofelectrocardiographs]. In the traditional 12-lead ECG, three limb leadsare defined as follows: lead I=LA-RA; lead II=LL-RA; lead III=LL-LA. Inthese equations, RA, LA, and LL denote the voltages of the right arm,left arm, and left leg, or body parts close to these limbs,respectively. Conventionally, in order to remove power lineinterference, a right leg (DRL) electrode is used. From therelationships above, one limb lead can be obtained from the other twolimb leads. For example, lead III=lead II-lead I. Three augmented limbleads are defined as follows: aVR=RA−(LA+LL)/2; aVL=LA−(RA+LL)/2;aVF=LL−(RA+LA)/2. Therefore, the three augmented limb leads can beobtained from two limb leads. For example, aVR=−(I+II)/2. Therefore,when two limb leads are measured, the remaining four leads can becalculated and obtained. Accordingly, the present invention discloses anapparatus for simultaneously measuring two leads using three electrodesand two amplifiers to provide six leads. Here, one amplifier means thatone signal is amplified. In an actual configuration, one amplifier maybe configured as a set of multiple cascaded amplification stages oractive filters. A standard 12-lead electrocardiogram consist of the sixleads and six precordial leads from V1 to V6.

Modified chest leads (MCLs) are similar to the precordial leads and aremedically very useful. In the principle of the present invention, thevoltage of one electrode that is not connected to any amplifier amongthe three electrodes is substantially equal to the circuit common in thesignal frequency band, as will be described later. Accordingly, theelectrocardiogram measurement apparatus 100 according to the presentinvention is suitable for measuring one MCL among six MCLs from MCL1 toMCL6. This is because each MCL is a voltage at the position of thecorresponding precordial lead referenced on the voltage of a body partto which the left hand is connected.

FIG. 3 illustrates a method for a user to measure MCL1 using theelectrocardiogram apparatus according to the present invention in an MCLmode. For example, in order to measure MCL1 using the electrocardiogramapparatus according to the present invention, the user contacts theelectrodes 111 and 112 provided on one surface of the electrocardiogrammeasurement apparatus 100 with both hands and brings the electrode 113provided on the other surface into contact with the MCL position (forexample, the V1 position in measuring MCL1), as shown in FIG. 3 . In thepresent invention, in order for the user to measure MCLn, the user needsto bring the electrode 113 into contact with the MCLn position, that is,the Vn position on the user's body.

Hereinafter, an embodiment of the electrocardiogram measurementapparatus according to the present invention will be described withreference to FIGS. 4 and 5 . FIG. 4 shows an electrical equivalentcircuit model for explaining principles and embodiments of removingpower line interference by the electrocardiogram measurement apparatusaccording to the present invention. FIG. 5 shows an electricalequivalent circuit model of an embodiment in which the electrocardiogrammeasurement apparatus according to the present invention simultaneouslymeasures two channels of an electrocardiogram using two single-endedinput amplifiers and one electrode driver.

In FIG. 4 , a current source 450 is used to model power lineinterference. In addition, in FIG. 4 , a human body is denoted by 430and modeled by three electrode resistors 431, 432, and 433 connected toeach other at one point. In FIG. 5 , one electrocardiogram signal ismodeled as one voltage source (461 or 462) existing between twoelectrode resistors. Since three electrodes are used in the presentinvention, in FIG. 5 , it is modelled such that there are two ECGvoltage sources 461 and 462 on the human body. This is because thoughthere are three electrocardiogram voltages on the three electrodes(because the number of cases of selecting two of the three electrodes is3), but only two electrocardiogram voltages are independent. Themodeling for power line interference in FIG. 4 and the electrocardiogramsignal in FIG. 5 is in a simplified form. However, the above models aresuitable to clarify issues to be addressed. In addition, the abovemodels clearly suggest what should be devised in the present invention.In addition, the present invention can be easily understood from theabove models. The present invention has been devised based on the abovemodels. Since the conventional arts do not use the above models, theconventional arts fail to accurately present a solution to the issues.

The present invention can be presented in various embodiments, as willbe described later. However, the various embodiments of the presentinvention are commonly based on the following principle of the presentinvention. The principle of the present invention is devised for thepresent invention. The present invention differs from the conventionalarts in that it does not use a DRL electrode compared to the DRL methodused in the conventional arts.

A challenge that has not been overcome by a conventionalelectrocardiogram measurement apparatus that does not use a DRLelectrode and is required to be overcome is to remove or reduce powerline interference. Power line interference in the electrocardiogrammeasurement apparatus is caused by a current source having asubstantially infinite output impedance due to a significantly highoutput impedance as shown in FIG. 4 (in FIG. 4 , the power lineinterference current source is indicated by 450.). Accordingly, in orderto remove the power line interference, it is necessary to minimize theimpedance looking into the human body from the power line interferencecurrent source. The impedance looking into the human body from the powerline interference current source is the sum of the impedance of thehuman body and the impedance of the electrocardiogram measurementapparatus. As a result, it is necessary to minimize the impedance of theelectrocardiogram measurement apparatus looking into through the threeelectrodes. There exists an impedance called an electrode impedance orelectrode resistance between each electrode used to measure theelectrocardiogram and the human body (431, 432, and 433 in FIG. 4 ).Accordingly, in order to minimize the effect of the electrode impedancewhen measuring an electrocardiogram voltage, the electrocardiogrammeasurement apparatus should have a high impedance. Accordingly, theelectrocardiogram measurement apparatus should satisfy two opposingconditions that a low impedance should be provided to remove power lineinterference and a high impedance should be provided to measure anelectrocardiogram voltage.

A method that can be considered to satisfy the two opposing conditions,for example, when three electrodes are used, is to connect three largeresistors to the three electrodes, respectively, combine the oppositeends of the three resistors at one point, and provide negative feedbackof the common mode signals of the three electrodes to the one point atwhich the three resistors are combined. However, this method ispractically difficult to use. This is because the impedance of the powerline interference current source is large and thus the magnitude of thepower line interference current will not decrease. Accordingly, in thiscase, the power line interference voltage induced in the three resistorsis still quite large or the amplifiers may be saturated. In addition,since the magnitude of the power line interference current is notreduced and the impedances of the respective electrodes may bedifferent, a different power line interference voltage is induced at ahigh level in each electrode. Accordingly, even if a differentialamplifier is used, it is difficult to remove the power line interferenceinduced in each electrode. This is the difficulty of the conventionalarts.

Therefore, in the present invention, the power line interference currentis concentrated and flows through only one of the electrodes installedin the electrocardiogram measurement apparatus. To this end, while threeelectrodes are connected to the human body, the impedance that the powerline interference current source looks into the electrocardiogrammeasurement apparatus through the one electrode is minimizes. Thereby,the power line interference voltage (indicated by 440 ν_(body) in FIG. 4) induced in the human body by the power line interference currentsource is minimized. Since the power line interference voltage inducedin the human body is minimized, the input impedances seen through theother electrodes of the electrocardiogram measurement apparatus may beincreased, and the electrocardiogram voltage may be accurately measured.At this point, what is important is that the one electrode through whichthe power line interference current flows should not be used formeasurement because a high power line interference voltage is induced atthe one electrode. Accordingly, in the present invention, when threeelectrodes are used, two electrodes and two amplifiers to receiveelectrocardiogram signals from the two electrodes are used formeasurement. In particular, it should be noted that two differentialamplifiers cannot be used in the electrocardiogram measurement apparatusemploying three electrodes because only two electrodes should be usedfor measurement. It should also be noted that, when negative feedback isused, if negative feedback is provided in all frequency bands then theelectrocardiogram signals appear at the electrode and mixed with thepower line interference voltage, and therefore negative feedback shouldbe provided only at the power line interference frequency. Hereinafter,the present invention will be described in detail with reference to thedrawings.

FIG. 4 and the subsequent drawings show only a part of theelectrocardiogram measurement apparatus 100 according to the presentinvention for simplicity. In FIG. 4 , the electrocardiogram measurementapparatus 100 according to the present invention comprises threeelectrodes 111, 112, and 113, two amplifiers 411 and 412, and oneelectrode driver (specifically, a band pass filter) 413. In FIGS. 4 and5 , the two amplifiers 411 and 412 employed in the present invention arenot differential amplifiers, but are single-ended input amplifiers.

An important feature of the embodiment of the present invention shown inFIG. 4 is that the electrocardiogram measurement apparatus 100 comprisesan electrode driver 413 represented as a band pass filter. That is, inFIG. 4 and the like, the electrode driver 413 may have a frequencycharacteristic of band pass. Accordingly, in the present invention, theelectrode driver 413 may be described as a band pass filter. The inputof the electrode driver 413 is connected to one electrode 112. Theoutput of the electrode driver 413 drives the electrode 113 through theresistor 423 (it is fed back to the electrode 113). The resonancefrequency or peak frequency of the electrode driver, that is, the bandpass filter 413, is the same as the frequency of power lineinterference. In addition, the band pass filter 413 has a large Q. InFIG. 4 , the input impedance of the band pass filter 413 is considerablylarge and the output impedance thereof is considerably small. Theelement value of the resistor 423 is represented by R_(o). In thepresent invention, for simplicity, the resistor 423 is regarded as theoutput impedance of the electrode driver 413.

In the present invention, two of the three electrodes are connected tothe circuit common of the analog circuit with the resistors 421 and 422,which have values R_(i). The resistors 421 and 422 are regarded as inputimpedances of the amplifiers 411 and 412.

In FIG. 4, 430 is a model of a human body. There is a contactresistance, commonly called electrode impedance, between the human bodyand an electrode. In FIG. 4 , the electrode impedances (electroderesistances) present between the human body 430 and the three electrodes111, 112, and 113 are represented by resistors 431, 432, and 433,respectively. The element values of the electrode resistors 431, 432,and 433 are indicated by R_(e1), R_(e2), and R_(e3), respectively.

In FIG. 4, 450 is a power line interference current source for modelingpower line interference. Current i_(n) of the power line interferencecurrent source 450 flows to the circuit common of the electrocardiogramapparatus 100 according to the present invention through the human body430 and the three electrodes 111, 112, and 113. When the power lineinterference currents flowing through the three electrodes 111, 112, and113 are represented by i_(n1), i_(n2), and i_(n3), the followingequation is established according to Kirchhoff's current law.

Equation 1i _(n) =i _(n1) +i _(n2) +i _(n3)  (1)

For circuit analysis, power line interference induced in the human body430 is denoted by ν_(body). In FIG. 4 , ν_(n1), ν_(n2), and ν_(n3)represent power line interference voltages at the electrodes 111, 112,and 113, respectively. In Equation 1, each current is given as follows.

$\begin{matrix}{{Equation}2} &  \\{i_{n1} = \frac{v_{body}}{R_{i} + R_{e1}}} & (2)\end{matrix}$ $\begin{matrix}{{Equation}3} &  \\{i_{n2} = \frac{v_{body}}{R_{i} + R_{e2}}} & (3)\end{matrix}$ $\begin{matrix}{{Equation}4} &  \\{i_{n3} = \frac{v_{body} + {v_{n2}{H(f)}}}{R_{o} + R_{e3}}} & (4)\end{matrix}$

Here,

$\begin{matrix}{{Equation}5} &  \\{v_{n2} = {\frac{R_{i}}{R_{i} + R_{e2}}v_{body}}} & (5)\end{matrix}$

Here, the transfer function of the band pass filter 413 is denoted by−H(f). Using the equations above, the following equation is obtained.

$\begin{matrix}{{Equation}6} &  \\{i_{n} = {\frac{v_{body}}{R_{i} + R_{e1}} + \frac{v_{body}}{R_{i} + R_{e2}} + {\frac{v_{body}}{R_{o} + R_{e3}}\frac{R_{i}}{R_{i} + R_{e2}}{H(f)}} + \frac{v_{body}}{R_{o} + R_{e3}}}} & (6)\end{matrix}$

In the present invention, the element values of the circuit of FIG. 4are used so that the following approximations are possible (Equations 7and 8). Equations 7 and 8 are important components of the presentinvention.

Equation 7R _(i) >>R _(e1) , R _(e2), or R _(e3)  (7)

Equation 8R _(i) >>R _(o)  (8)

Then, the following approximation is established.

$\begin{matrix}{{Equation}9} &  \\{i_{n} \approx {\frac{v_{b}}{R_{o} + R_{e3}}\left( {1 + {H(f)}} \right)}} & (9)\end{matrix}$

The following equation is obtained from Equation 9.

$\begin{matrix}{{Equation}10} &  \\{v_{body} \approx {\left( {R_{o} + R_{e3}} \right)\frac{i_{n}}{1 + {H(f)}}}} & (10)\end{matrix}$

In Equation 10, if there is no feedback, that is, H(f)=0, the followingequation is established.

Equation 11ν_(body)≈(R _(o) +R _(e3))i _(n) if H(f)=0.  (11)

By comparing Equation 10 and Equation 11, it can be seen that thepresent invention reduces the influence of power line interferencecurrent i_(n) to the amount of feedback, or (1+H(f)). Therefore, if themagnitude of the gain at the resonance frequency of the band pass filtersatisfies |H(f_(o))|>>1, ν_(body)≈0. Thus, the principle of removingpower line interference in the present invention has been proved.

Using Equations 2 and 10, the following can be confirmed.

$\begin{matrix}{{Equation}12} &  \\{v_{n1} \approx {\frac{R_{i}}{R_{i} + R_{e1}}\left( {R_{o} + R_{e3}} \right)\frac{i_{n}}{1 + {H(f)}}} \approx {\left( {R_{o} + R_{e3}} \right)\frac{i_{n}}{1 + {H(f)}}} \approx v_{body}} & (12)\end{matrix}$

Now the following result is obtained for ν_(n3). From the above results,ν_(body)≈0 and i_(n3)?aai_(n) can be used.

Equation 13ν_(n3)≈ν_(body) −i _(n3) R _(e3) ≈−i _(n) R _(e3)  (13)

The following can be derived from Equations 12 and 13.

Equation 14|ν_(n3)|>>|ν_(n1)|  (14)

This means that, if |H(f)| is large, as a result of feedback, almost allpower line interference current flows through the electrode (theelectrode 113 in FIG. 4 ) to which feedback is provided, and thereforethe electrode to which feedback is provided is contaminated by powerline interference while the electrodes (the electrodes 111 and 112 inFIG. 4 ) to which feedback is not provided are hardly influenced bypower line interference. This in turn means that only the electrodes towhich feedback is not provided should be used for electrocardiogrammeasurement and the electrode to which feedback is provided should notbe used for the measurement. Accordingly, the effect of power lineinterference cannot be eliminated using a differential amplifier whoseinput is connected to the electrodes 111 and 113 or a differentialamplifier whose input is connected to the electrodes 112 and 113. Thisis one of the important issues of the conventional arts.

Hereinafter, description will be given of the principle of obtaining twoelectrocardiogram channel signals using three electrodes according tothe present invention. FIG. 5 shows an electrical equivalent circuitgiven when an electrocardiogram is measured using the electrocardiogramapparatus according to the present invention.

In FIG. 5 , ν₁, ν₂, and ν₃ represent the electrocardiogram signalvoltages of the electrodes 111, 112, and 113, respectively. Voltage ν₂of the electrode 112 obtained by analyzing this equivalent circuit basedon the principle of superposition is given as follows.

$\begin{matrix}{{Equation}15} &  \\{v_{2} = {{{- v_{a}}\frac{\left( {R_{o} + R_{e3}} \right){\left( {R_{i} + R_{e2}} \right)}}{\left( {R_{i} + R_{e1}} \right) + {\left( {R_{o} + R_{e3}} \right){\left( {R_{i} + R_{e2}} \right)}}}\frac{R_{i}}{\left( {R_{i} + R_{e2}} \right)}} + {v_{b}\frac{\left( {R_{i} + R_{e1}} \right){\left( {R_{i} + R_{e2}} \right)}}{\left( {R_{i} + R_{e1}} \right){{\left( {R_{i} + R_{e2}} \right) + \left( {R_{i} + R_{e1}} \right)}}}\frac{R_{i}}{\left( {R_{i} + R_{e2}} \right)}} - {v_{2}{H(f)}\frac{\left( {R_{i} + R_{e1}} \right){\left( {R_{i} + R_{e2}} \right)}}{\left( {R_{o} + R_{e3}} \right) + {\left( {R_{i} + R_{e1}} \right){\left( {R_{i} + R_{e2}} \right)}}}\frac{R_{i}}{\left( {R_{i} + R_{e2}} \right)}}}} & (15)\end{matrix}$

In Equation 15, the symbol ∥ represents the value of parallelresistance. As in the previous equations, the conditions of Equations 7and 8 can be assumed. In this case, voltage ν₂ is approximated asfollows.

$\begin{matrix}{{Equation}16} &  \\{v_{2} \approx {{{- v_{a}}\frac{\left( {R_{o} + R_{e3}} \right)}{\left( {R_{i} + R_{e3}} \right)}\frac{R_{i}}{\left( {R_{i} + R_{e2}} \right)}} + v_{b} - {v_{2}{H(f)}}} \approx {v_{b} - {v_{2}{H(f)}}}} & (16)\end{matrix}$

Accordingly, under the conditions of Equations 7 and 8, voltage ν₂ isgiven as follows.

$\begin{matrix}{{Equation}17} &  \\{v_{2} \approx {v_{b}\frac{1}{1 + {H(f)}}}} & (17)\end{matrix}$

From the above equation, it can be seen that if |H(f₀)|<<1, ν₂≈ν_(b) inthe signal band.

FIG. 6 shows a frequency response of the band pass filter used in theelectrocardiogram measurement apparatus according to the presentinvention. In FIG. 6 , the resonance frequency of the band pass filteris 60 Hz, the gain at the resonance frequency is 20, and Q=120. FIG. 7shows that when the band pass filter of FIG. 6 is used, ν_(b) may beobtained with an accuracy of 98% at a frequency less than or equal to 40Hz.

Similarly, voltage ν₁ of the electrode 1 is obtained as follows.

$\begin{matrix}{{Equation}18} &  \\{v_{1} = {{{+ v_{a}}\frac{R_{i}}{\left( {R_{i} + R_{e1}} \right) + {\left( {R_{o} + R_{e3}} \right){\left( {R_{i} + R_{e2}} \right)}}}} + {v_{b}\frac{\left( {R_{i} + R_{e1}} \right){\left( {R_{i} + R_{e2}} \right)}}{\left( {R_{o} + R_{e3}} \right) + {\left( {R_{i} + R_{e1}} \right){\left( {R_{i} + R_{e2}} \right)}}}\frac{R_{i}}{\left( {R_{i} + R_{e1}} \right)}} - {v_{2}{H(f)}\frac{\left( {R_{i} + R_{e1}} \right){\left( {R_{i} + R_{e2}} \right)}}{\left( {R_{o} + R_{e3}} \right) + {\left( {R_{i} + R_{e1}} \right){\left( {R_{i} + R_{e2}} \right)}}}\frac{R_{i}}{\left( {R_{i} + R_{e1}} \right)}}}} & (18)\end{matrix}$

When the conditions of Equations 7 and 8 are used, voltage ν₁ isapproximated as follows.

Equation 19ν₁≈+ν_(a)+ν_(b)−ν₂ H(f)≈ν_(a)+ν₂

The equation above is obtained using Equation 16. Equation 20 below isobtained from the equation above, and ν_(a) may be obtained by thisequation. It can be seen from Equation 20 that ν_(a) can be obtainedwithout the influence of the band pass filter.

Equation 20ν₁−ν₂≈+ν_(a)  (20)

Thus, the principle of obtaining signals of two electrocardiogramchannels using two single-ended amplifiers according to the presentinvention has been described.

FIG. 8 shows an electrical equivalent circuit model for explaining theprinciple and embodiment of removing power line interference by theelectrocardiogram measurement apparatus according to the presentinvention using common mode signal of two electrodes. Of course, evenwhen the common mode signal is used, the power line interference currentis concentrated and flows through an electrode 832 to which the outputof an electrode driver 813 is fed back, and a power line interferencevoltage is present in the electrode 832. FIG. 9 shows an electricalequivalent circuit model of an embodiment of simultaneously measuringtwo channels of an electrocardiogram using one differential amplifier811 and one single-ended input amplifier 812 while removing power lineinterference using the method of FIG. 8 , that is, adopting common modesignal. As in the previous case where two single-ended input amplifiersare used, two electrocardiogram voltages may be obtained.

For simplicity, the circuit analysis of FIGS. 8 and 9 is omitted. In theembodiment of FIGS. 8 and 9 , one electrode driver, that is, the bandpass filter 813, applies a driving voltage to a human body part incontact with the electrode 112 through the output impedance R_(o) andthe electrode 112, as in the embodiment of FIGS. 4 and 5 . That is, theelectrode 112 is not connected to an amplifier for measuring theelectrocardiogram voltage, but is connected to the electrode driver 813through the output impedance 823. That is, the electrode 112 is not usedin measuring the electrocardiogram voltage. When the peak value of theband pass filter is large, the transfer function H(f) of the band passfilter may be corrected or compensated for in order to realize |H(f)|<<1in the signal band.

While one band pass filter 813 is used as one electrode driver in FIG. 8, one constant voltage source 1013 is used as one electrode driver inFIG. 10 . The constant voltage source 1013 applies a driving voltage toa human body part in contact with the electrode 112 through a resistor1023 having a small resistance R_(o) and the electrode 112. Most of thepower line interference current flows through the electrode 112. Inorder to further concentrate the power line interference current, theoutput impedance 1023 of the electrode driver 1013 may be reduced. Thismethod is less effective in removing power line interference than theprevious methods using a band pass filter. Even in the embodiment ofFIG. 10 , two electrocardiogram voltages are simultaneously amplifiedusing two amplifiers connected to two electrodes except for theelectrode in which power line interference current is concentrated. Inthe embodiment of FIG. 10, one differential amplifier 1011 and onesingle-ended input amplifier 1012 are used. The output of thesingle-ended input amplifier 1012 may include weak power lineinterference and a band pass filter 1033 may be used to further reducepower line interference.

In FIGS. 5, 9 and 10 , it is important to drive one electrode using anelectrode driver having a small output impedance in order to reduce thepower line interference. The output of the electrode driver istransmitted, through the electrode, to a human body part that is incontact with the electrode. Once the power line noise is reduced, twosingle-ended input amplifiers may be used or one single-ended inputamplifier and one differential amplifier to amplify the twoelectrocardiogram voltages received from the two electrodes.

The principle of the present invention is summarized as follows. Thecondition that the input impedance the power line interference currentsource looks into the electrocardiogram measurement apparatus should below is satisfied by reducing the output impedance of the electrodedriver connected to one electrode, and the condition that the inputimpedances the electrocardiogram signal voltages are looking into theelectrocardiogram measurement apparatus should be high is satisfied byincreasing the input impedances seen through the other two electrodes.Thereby, the electrocardiogram measurement apparatus according to thepresent invention may accurately measure the electrocardiogram signalvoltage while reducing power line interference. Accordingly, the outputimpedance of the electrode driver of the electrocardiogram measurementapparatus according to the present invention is less than the inputimpedance of each of the two amplifiers.

Description has been given above regarding an embodiment in which powerline interference is removed by applying the output of one electrodedriver to one electrode, and two electrocardiogram voltages are measuredsimultaneously using two amplifiers of a large input impedance thatreceive two electrocardiogram voltages from two electrodes.

The electrocardiogram measurement apparatus according to the presentinvention provides six electrocardiogram leads obtained simultaneouslyusing the smallest number of electrodes (specifically, threeelectrodes). When the electrocardiogram measurement apparatus accordingto the present invention is used in the MCL mode, one limb lead(specifically, Lead I) and one MCL may be measured.

Since the portable electrocardiogram measurement apparatus according tothe present invention has a size of one credit card, it is convenient tocarry the apparatus, and multiple electrocardiograms may be obtainedmost conveniently regardless of time and place. In addition, since theelectrocardiogram measurement apparatus according to the presentinvention is capable of wirelessly communicating with a smartphone, theelectrocardiogram measurement apparatus may be conveniently used withoutsubstantial limitation on the distance between the electrocardiogrammeasurement apparatus and the smartphone.

In addition, when the electrocardiogram measurement apparatus accordingto the present invention is not in use, all circuits except the currentdetectors are turned off and only the microcontroller enters a sleepmode. When the electrocardiogram measurement apparatus is used, onlynecessary circuits are supplied with power, and the microcontrollerenters an activation mode. Therefore, consumption of power of thebattery embedded in the electrocardiogram measurement apparatus may bereduced to the maximum degree.

In addition, the electrocardiogram measurement apparatus according tothe present invention does not include a mechanical power switch or aselection switch. Accordingly, the measurement apparatus may be designedto be compact and slim, and may not lead to unnecessary troublesome useof a switch by the user, failure and finite service life of the switch,or an increase in manufacturing cost.

Further, since the electrocardiogram measurement apparatus according tothe present invention does not include a display such as an LCD, theremay no possibility of failure and deterioration of the display, and theapparatus may not lead to an increase in manufacturing cost, and may bemanufactured in a compact size and convenient to carry.

DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an electrocardiogram measurementapparatus having three electrodes according to the present invention.

FIG. 2 illustrates a method for measuring an electrocardiogram in a6-channel mode using the electrocardiogram measurement apparatus 100according to the present invention.

FIG. 3 illustrates a method for measuring an electrocardiogram in an MCLmode using the electrocardiogram apparatus according to the presentinvention.

FIG. 4 shows an electrical equivalent circuit model for explaining theprinciple and embodiment of removing power line interference by theelectrocardiogram measurement apparatus according to the presentinvention.

FIG. 5 shows an electrical equivalent circuit model of an embodiment inwhich the electrocardiogram measurement apparatus according to thepresent invention simultaneously measures two channels of anelectrocardiogram using two single-ended input amplifiers and one bandpass filter (electrode driver).

FIG. 6 shows a frequency response of the band pass filter used as anelectrode driver in the electrocardiogram measurement apparatusaccording to the present invention.

FIG. 7 shows a frequency response of one signal channel when a band passfilter is used as an electrode driver in the electrocardiogrammeasurement apparatus according to the present invention.

FIG. 8 shows an electrical equivalent circuit model for explaining theprinciple and embodiment of removing power line interference by theelectrocardiogram measurement apparatus according to the presentinvention using the common mode signal.

FIG. 9 shows an electrical equivalent circuit model of an embodiment ofsimultaneously measuring two channels of an electrocardiogram by theelectrocardiogram measurement apparatus according to the presentinvention, using one differential amplifier, one single-ended inputamplifier and one band pass filter (electrode driver) in removing powerline interference using the common mode signal.

FIG. 10 is another embodiment of simultaneously measuring two channelsof an electrocardiogram by the electrocardiogram measurement apparatusaccording to the present invention using one differential amplifier, onesingle-ended input amplifier, and one constant voltage generator(electrode driver).

FIG. 11 is a block diagram of a circuit embedded in theelectrocardiogram measurement apparatus according to the presentinvention.

FIG. 12 is an operation flowchart of the electrocardiogram measurementapparatus according to the present invention.

FIG. 13 shows an initial screen of a smartphone when a smartphone app isexecuted to use the electrocardiogram measurement apparatus according tothe present invention

FIG. 14 is a flowchart illustrating a smartphone app operated when theelectrocardiogram measurement apparatus according to the presentinvention is used.

FIG. 15 shows an electrocardiogram measurement apparatus according tothe present invention provided with a blood test strip insert port

FIG. 16 shows an example of implementing the electrocardiogrammeasurement apparatus according to the present invention in the form ofa smart watch.

FIG. 17 shows an example of implementing the electrocardiogrammeasurement apparatus according to the present invention in the form ofa ring.

FIGS. 18 and 19 show examples of the electrocardiogram measurementapparatus configured to be coupled to pants to measure anelectrocardiogram according to the present invention.

FIGS. 20 and 21 show embodiments of the electrocardiogram measurementapparatus that can be coupled to the band of a watch using two or oneslide guide that serves as two or one electrode according to the presentinvention.

FIG. 22 is a perspective view of an electrocardiogram measurementapparatus having four electrodes according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment according to the present invention will bedescribed with reference to the drawings. In this embodiment, anelectrocardiogram (ECG) measurement apparatus is described as includingthree electrodes, but is not limited thereto. The electrocardiogrammeasurement apparatus may include three or more electrodes. An importantembodiment of the present invention has been described above based onFIGS. 4 to 10 to explain the principle of the present invention.

The portable electrocardiogram measurement apparatus according to thepresent invention may be in the form of a credit card and have athickness of 6 mm or less in order to enhance portability. Since theportable electrocardiogram measurement apparatus according to thepresent invention is portable, it uses a battery. When a CR2032 typebattery is employed, the service life thereof may be about 2 years.

In addition, to make the portable electrocardiogram measurementapparatus compact, either a mechanical power switch or a selectionswitch may not be provided. In addition, to reduce power consumption, adisplay is not employed.

The portable electrocardiogram measurement apparatus according to thepresent invention may employ a current detector in order not to use amechanical power switch or a selection switch. The current detector isalways supplied with power required for operation and waits to generatean output signal when an event occurs. When a user brings multipleelectrodes into contact with the body to measure an electrocardiogram, aloop of minute current that can flow through the human body isgenerated. Accordingly, when the body is electrically connected to thecurrent detector, the current detector causes the minute current to flowthrough the body. Upon detecting the minute current, the currentdetector generates an output signal. When the portable electrocardiogramapparatus is not in use, only the current detector operates, and theother circuits are powered off, and the microcontroller waits in a sleepmode in order to increase the battery usage time. At this time, when anevent of touching two electrodes by both hands occurs and the currentdetector generates an output signal, the microcontroller is activated topower on the electrocardiogram circuit to perform electrocardiogrammeasurement. The current detected by the current detector is suppliedfrom the battery provided in the portable electrocardiogram measurementapparatus, and is a direct current.

The electrocardiogram measurement apparatus 100 according to the presentinvention may further include a function of measuring blood propertiessuch as blood glucose level, ketone level, or international normalizedratio (INR). Accordingly, in this embodiment, the electrocardiogrammeasurement apparatus 100 will be described as an example for measuringan electrocardiogram and blood properties together. The blood glucoselevel or ketone level may be measured using an amperometric technique.The INR is a measure of the tendency to coagulate blood and may bemeasured for capillary blood using an electric impedance technique, theamperometric technique, a mechanical technique, or the like. One bloodtest strip insert port through which a blood test strip required for theblood property test can be inserted may be provided in the case of theelectrocardiogram measurement apparatus according to the presentinvention.

In an embodiment of the electrocardiogram measurement apparatus 100according to the present invention, a thermometer function may beincluded. A suitable type to include the thermometer function in theelectrocardiogram measurement apparatus 100 according to the presentinvention is a contact type, and a suitable temperature sensor is athermistor. In order to measure body temperature using theelectrocardiogram measurement apparatus 100 including the thermometerfunction according to the present invention, a user brings a portion ofthe electrocardiogram measurement apparatus 100 to which the temperaturesensor is attached into contact with the user's forehead or armpit. Toaccurately measure the body temperature, the temperature of the skinshould not be changed by the portion of the electrocardiogrammeasurement apparatus 100 to which the temperature sensor is attached.

FIG. 11 is a block diagram of a circuit embedded in theelectrocardiogram measurement apparatus according to the presentinvention. Although not shown in FIG. 11 for clarity of the invention,the electrocardiogram measurement apparatus according to the presentinvention may include a blood test circuit and a blood test strip insertport. The function and operation of each block in FIG. 11 are describedbelow. When the user touches a pair of electrodes 111 and 112 with bothhands, an electrocardiogram current detector 1140 allows minute currentto flow through both hands and detects the minute current flowingthrough both hands. Then, the current detector 1140 generates a signalto change the microcontroller 1180 from a sleep mode to an active mode.Then, the microcontroller 1180 powers on the electrocardiogrammeasurement circuit 1160 and the AD converter 1170. Theelectrocardiogram measuring circuit 1160 amplifies two electrocardiogramsignals through two amplifiers and generates two outputs. The ADconverter 1170 receives the two outputs of the electrocardiogrammeasurement circuit 1160, and the outputs of the AD converter 1170 aretransmitted to the smartphone 210 through the wireless communicationmeans 1190 and the antenna 1192. Upon receiving data, the smartphone 210displays multiple electrocardiogram waveforms. After the measurement fora certain duration, the microcontroller 1180 enters the sleep mode andwaits for the next touch of both hands.

When the electrocardiogram measurement apparatus according to thepresent invention is brought into contact with both hands and the lowerleft abdomen, six leads can be displayed at a time. However, when it isinconvenient to bring the electrocardiogram measurement apparatus intocontact with the lower left abdomen or only one lead is to be measured,the electrocardiogram measurement apparatus may automatically determinewhether the user intends to measure only one lead or six leads. When theuser touches the electrocardiogram measurement apparatus with only bothhands to measure only one lead, only one current detector 1140 detectscurrent. Then, only Lead I is displayed on the smartphone. When the usertouches the electrocardiogram measurement apparatus with both hands andthe lower left abdomen to measure six leads, both the current detector1140 and the current detector 1150 detect currents. The six leads arethen displayed on the smartphone. Each of the blocks shown in FIG. 11may be implemented based on conventional technology using commercializedparts.

FIG. 12 is an operation flowchart of the electrocardiogram measurementapparatus 100 according to the present invention in measuring anelectrocardiogram. In order to measure the electrocardiogram, a usertouches the pair of electrodes 111 and 112 of the electrocardiogrammeasurement apparatus 100 with both hands (1210). Then, the currentdetector detects minute current flowing through the human body betweenboth hands and generates an output signal (1215). The output signalactivates the microcontroller 1180 by generating an interrupt of themicrocontroller 1180 (1220). The activated microcontroller 1180activates the wireless communication means 1190. Hereinafter, a casewhere the wireless communication means 1190 is a Bluetooth low energydevice will be described. The wireless communication means 1190 of theelectrocardiogram measurement apparatus 100 advertises as a Bluetoothlow energy peripheral (1225). At this time, the smartphone that isperforming scanning as a Bluetooth low energy central device discoversthe electrocardiogram measurement apparatus 100 and attempts to connectthereto. At this time, when the electrocardiogram measurement apparatus100 approves the connection, the smartphone and the electrocardiogrammeasurement apparatus 100 are Bluetooth low energy connected (1230). Atthis time, the electrocardiogram measurement apparatus 100 may checkwhether the user has touched the electrocardiogram measurement button ofthe smartphone to actually measure an electrocardiogram (1235).

Once it is confirmed that electrocardiogram measurement is requested,the microcontroller 1180 powers on the electrocardiogram measurementcircuit 1160 (1240). This operation may be performed by connecting anoutput pin of the microcontroller 1180 to the electrocardiogrammeasurement circuit 1160 and setting the voltage of the output pin toHigh. Next, it is checked whether the pair of electrodes 111 and 112 arein touch with both hands, using the current detector (1245). This stepis to determine when the microcontroller 1180 should start ECGmeasurement, that is, AD conversion. That is, this step is to checkwhether both hands continuously remain in contact with the electrodes111 and 112.

After the above steps, the microcontroller 1180 starts the ECGmeasurement (1250). That is, the microcontroller 1180 performs ADconversion according to a preset AD conversion cycle and brings an ADconversion result. In the present invention, two electrocardiogramsignals are measured. The measured ECG data is transmitted to thesmartphone 210 (1255). When a preset measurement time of, for example,30 seconds, elapses, the microcontroller 1180 enters the sleep mode(1260).

All circuits of FIG. 11 are driven by a battery embedded in theelectrocardiogram measurement apparatus 100. In the example of FIG. 11 ,any of a mechanical power switch, a mechanical selection switch, and adisplay may not be provided. In FIG. 11 , when the electrocardiogrammeasurement apparatus 100 does not perform measurement, theelectrocardiogram current detector and the microcontroller 1180 eachconsume approximately 1 uA, and all the other blocks are completelypowered off.

The electrocardiogram measurement apparatus 100 according to the presentinvention is used together with the smartphone 210. FIG. 13 shows aninitial screen of a smartphone when a smartphone app according to thepresent invention is executed. When the smartphone app is executed,touch buttons 1331, 1332, 1334, 1336, 1342, 1344, 1346, and 1350 aredisplayed on the display 1320 of the smartphone 210. The buttons 1331,1332, 1334, and 1336 related to the electrocardiogram are configured inan electrocardiogram box 1330. When the electrocardiogram measurementapparatus 100 according to the present invention includes a function ofmeasuring blood properties, the buttons 1342, 1344 and 1346 related toblood properties are configured in a blood glucose box 1340. To measurean electrocardiogram, the user selects and touches one of theelectrocardiogram measurement mode buttons 1331 and 1332 wanted. Whenthe user is to measure the electrocardiogram in a 6-channel mode, theuser touches the button 1331. When the user is to measure theelectrocardiogram in an MCL mode, the user touches the button 1332.Then, when the user remains touching the pair of electrodes 111 and 112of the electrocardiogram measurement apparatus 100 with both hands, theelectrocardiogram measurement apparatus 100 measures theelectrocardiogram as described above. The measured ECG data is displayedin the form of a chart on the smartphone display 1320 and is stored inthe smartphone 210. The open button 1334 is touched to view, in a chartform, the ECG measurement data stored in the past. To send the storeddata to a doctor or a hospital, the Send button 1336 is touched. TheSetting button 1350 is touched when a user's name, date of birth,gender, address, etc. are to be recorded or when options are to be set.

FIG. 14 is a flowchart illustrating a smartphone app according to thepresent invention. For simplicity, only the process of measuring anelectrocardiogram will be described. As shown in FIG. 14 , the flowoperated in measuring the electrocardiogram is composed of two branches:a central branch 1422, 1424, 1426, 1428, 1430, 1432, and a Bluetooth lowenergy (BLE) branch 1452, 1454. When the app starts, various buttonsappear on the smartphone display 1320 (1410), and then the BLE branch1452 1454 for performing Bluetooth low energy communication is started.The user who wants to measure the electrocardiogram touches one of theECG measurement buttons 1331 and 1332 (1422).

When the user touches one of the ECG measurement buttons 1331 or 1332(1422), an ECG measurement request signal is sent to the BLE branch1452, 1454 (1424). In addition, a message instructing the user tocontact electrodes according to the ECG measurement mode is displayed onthe smartphone display 1320 (1424). In the BLE branch 1452, 1454, an ECGmeasurement request signal is sent to the electrocardiogram measurementapparatus 100 (1454).

The electrocardiogram measurement apparatus 100 receiving the ECGmeasurement request signal performs the electrocardiogram measurementtask described in FIG. 12 and transmits measured ECG data to the BLEbranch 1452, 1454. The BLE branch 1452, 1454 transfers the ECG datareceived from the electrocardiogram measurement apparatus 100 to thecentral branch 1422, 1424, 1426, 1428, 1430, 1432. Then, the centralbranch 1422, 1424, 1426, 1428, 1430, 1432 receives the ECG data (1426).The received ECG data is displayed in a chart form on the smartphonedisplay 1320 in the central branch 1422, 1424, 1426, 1428, 1430, 1432(1428). When all the ECG measurements are completed, the measured ECGdata is stored in a file format in a smartphone storage device (1430).While the measured ECG data is being displayed in the form of a chart onthe smartphone display 1320, the smartphone app waits for the user toend the app by pressing the app exit button (1432).

According to the present invention, the user may be provided withdesired results without undergoing abnormality in the number of cases ofall possible operation sequences by using the electrocardiogrammeasurement apparatus 100, which is not provided with a mechanicalswitch, a selection switch, or a display, and a smartphone appsimplified to use.

The present invention has been described in detail regarding a casewhere an electrocardiogram is measured using the single portableelectrocardiogram measurement apparatus 100 and a smartphone app, butthe electrocardiogram measurement apparatus 100 according to the presentinvention is not limited thereto. Various measurement items may beadditionally measured.

As described above, the electrocardiogram measurement apparatus 100according to the present invention may further include a function ofmeasuring blood properties. In this case, one embodiment of theelectrocardiogram measurement apparatus 1500 to which the function ofmeasuring blood properties is added according to the present inventionincludes a blood property test strip insert port 1510 through which ablood property test strip 1520 can be inserted, and one type thereof maybe configured as shown in FIG. 15 .

The electrocardiogram measurement apparatus 100 according to the presentinvention has been described as being implemented in a plate shape.However, the electrocardiogram measurement apparatus according to thepresent invention uses the minimum number of filters in principle andhas a simple circuit configuration, and accordingly it can bemanufactured in a compact size. Accordingly, the electrocardiogrammeasurement apparatus according to the present invention has a featurethat the power consumption of the battery is low. Accordingly, theelectrocardiogram measurement apparatus according to the presentinvention is suitable to be implemented as a watch or ring shape.Particularly, when the electrocardiogram measurement apparatus accordingto the present invention is implemented as a watch shape or a ringshape, it is suitable for a user to always wear and has an advantagethat it can be used in conjunction with a photoplethysmograph (PPG).

The PPG uses LEDs to emit light to the skin and measure reflected ortransmitted light. Recently, the PPG built in the smart watch canprovide heart rate, heart rate variability (HRV), and breathing rate(BR). HRV provides a lot of information about personal healthconditions. HRV is used for sleep analysis or stress analysis, and isalso used to detect arrhythmias such as atrial fibrillation. Normally,HRV analysis is performed using ECG. However, recently, it has also beenperformed using PPG. The PPG included in a patient monitor used inhospitals measures oxygen saturation and generates an alarm when theoxygen saturation is low. Recently, a PPG signal is obtained using acamera installed in a smartphone, and the occurrence of an arrhythmiasymptom may be detected using the signal. Accordingly, PPG installed onthe watch or ring facilitates detection of occurrence of an arrhythmiasymptom. Accordingly, when the PPG and the electrocardiogram measurementapparatus according to the present invention are installed together on awatch or ring, the PPG may generate an alarm signal upon detectingoccurrence of arrhythmia symptoms, and the user who receives the alarmsignal can measure the electrocardiogram using the electrocardiogrammeasurement apparatus according to the present invention.

For user convenience and accuracy of ECG measurement, the locations ofthe electrocardiogram electrodes are important. A plurality of examplesof implementing the electrocardiogram measurement apparatus according tothe present invention on a watch will be described with reference toFIG. 16 .

In the first example, three ECG electrodes may be installed on bothsides of a watch band. In FIG. 16 , one ECG electrode 111 is installedon the inner surface of the band, i.e., the surface of the bandcontacting the wrist, and the two electrodes 112 and 113 are installedon the outer surface of the band, i.e., the surface of the band thatdoes not contact the wrist. In this example, when the user wears thewatch on the left wrist, the electrode 111 contacts the left wrist. Inthis case, the user brings the electrode 112 into contact with the leftlower abdomen or chest and the right hand finger into contact with theelectrode 113 to perform ECG measurement.

In the second example, one ECG electrode 1610 may be installed on thebottom surface of the watch. In this case, the electrode 1610 is alwaysin contact with the wrist wearing the watch. When the user is to measurethe ECG, the electrode 112 is brought into contact with the left lowerabdomen or chest, and the electrode 113 is brought into contact with onefinger of the hand without the watch.

In the third example, another part of the watch body, for example 1640,may be used instead of the electrode 113 of FIG. 16 .

In all the above cases where electrodes are installed on a watch orwatch band for user convenience and accuracy of electrocardiogrammeasurement, it should be noted that one electrode 112 is installed onthe outer surface, that is, the surface of the band that does notcontact the wrist, of a portion of the band located on the inside of thewrist (the palm side, not the back side of the hand). This is intendedto make the electrode 112 comfortably contact the user's left lowerabdomen or chest portion. In addition, in all the above cases whereelectrodes are installed on a watch or watch band, the PPG 1630installed on the bottom surface of the watch may analyze the PPG signaland generate an alarm to the user.

The electrocardiogram measurement apparatus according to the presentinvention may be implemented in a ring shape. In this case, the ring isworn on the thumb or little finger to facilitate electrocardiogrammeasurement. FIG. 17 shows an example in which the electrocardiogrammeasurement apparatus according to the present invention is implementedin a ring shape. In FIG. 17 , one electrode 111 among the threeelectrodes contacts a finger wearing the ring. The electrode 112 andelectrode 113 are not in contact with the finger. That is, the electrode112 and the electrode 113 are located on the outer portion of the thumbor little finger, and are arranged spaced apart from each other. Whenthe ring is worn on the thumb of the left hand, the electrode 111 may bebrought into contact with the thumb of the left hand, the electrode 112may be brought into contact with the lower left abdomen, and theelectrode 113 may be brought into contact with the second finger of theright hand. PPG 1730 installed on the surface of the ring that touchesthe skin may analyze the PPG signal and generate an alarm to the user.

The electrocardiogram measurement apparatus according to the presentinvention may be implemented in a form that is easy to be coupled toother objects to keep the apparatus worn on a body. FIGS. 18 and 19 showexamples of the electrocardiogram measurement apparatus according to thepresent invention that can be coupled to pants and measure anelectrocardiogram immediately when the electrocardiogram is be measured.In FIG. 18 , two clips 111 and 112 serving as two electrodes are used toattach the electrocardiogram measurement apparatus 100 according to thepresent invention to the inside of the pants, that is, between the pantsand the user's body. When used, the electrocardiogram measurementapparatus 100 is attached to the pants at the position of the lower leftabdomen using the clips 111 and 112. Then, the electrode 113 and the PPG1830 automatically contact the lower left abdomen of the user. When thePPG 1830 sends an alarm or ECG measurement is needed, the user brings aleft hand finger into contact with the clip 111 and brings a right handfinger into contact with the clip 112.

The electrocardiogram measurement apparatus 100 according to the presentinvention shown in FIG. 19 is attached to the outside of the pants. Theelectrocardiogram measurement apparatus 100 and the clip 113 inside thepants press the pants, and thus the electrocardiogram measurementapparatus 100 is fixed to the pants. When the electrocardiogram ismeasured, the clip 113 automatically contacts the user's lower leftabdomen, and the user brings a left hand finger into contact with theelectrode 111 and brings a right hand finger into contact with theelectrode 112.

FIGS. 20 and 21 show embodiments of the electrocardiogram measurementapparatus that can be coupled to the band of a watch using two or oneslide guide that serves as an electrode according to the presentinvention. In FIG. 20 , when a watch band is inserted between theelectrocardiogram measurement apparatus 100 according to the presentinvention and the slide guides 112 and 113 serving as electrodes, theelectrocardiogram measurement apparatus 100 is fixed to the watch band.When the watch is worn on the left hand, the electrode 111 and the PPG2030 automatically contact the left wrist. When the PPG 2030 sends analarm or ECG measurement is needed, the user brings the lower leftabdomen into contact with the slide guide 113 and brings a right handfinger into contact with the slide guide 112.

In FIG. 21 , when the band of the watch is inserted between theelectrocardiogram measurement apparatus 100 according to the presentinvention and the slide guide 111, the electrocardiogram measurementapparatus 100 is fixed to the band of the watch. When the watch is wornon the left hand, the electrode 111 automatically contacts the leftwrist. In order to measure the ECG, the user brings the lower leftabdomen into contact with the electrode 113 and brings a right handfinger into contact with the electrode 112.

As described above, the electrocardiogram measurement apparatusaccording to the present invention to which the PPGs 1830 and 2030 ofFIGS. 18 and 20 are added is capable of constantly monitoring a user'sheart rate. Although a separate drawing is not added for simplicity, itis apparent that the electrocardiogram measurement apparatus accordingto the present invention can be coupled to the band of a watch using theclips shown in FIG. 18 or 19 instead of the slide guides shown in FIGS.20 and 21 .

In the embodiment of the electrocardiogram measurement apparatusaccording to the present invention, the electrocardiogram measurementapparatus 100 is described as including three electrodes. However, inanother embodiment according to the present invention, theelectrocardiogram measurement apparatus may include four electrodes. Theoperation principle of an electrocardiogram measurement apparatusincluding the four electrodes according to the present invention is thesame as that of the previous case of including three electrodes. Theimportant point is that the electrocardiogram measurement apparatusincluding four electrodes according to the present invention includesthree amplifiers configured to receive an ECG signal from threeelectrodes, the three amplifiers each amplify one ECG signal, andaccordingly the apparatus actually measures three ECG signalssimultaneously.

The electrocardiogram measurement apparatus including the fourelectrodes may be easily implemented by the foregoing description. Themethod of using the electrocardiogram measurement apparatus includingthe four electrodes according to the present invention is almost thesame as the method of using the electrocardiogram measurement apparatus100 including the three electrodes according to the present invention.The three ECG signals measured by the electrocardiogram measurementapparatus including four electrodes according to the present inventioninclude, for example, two limb leads and one MCL. Alternatively, thethree ECG signals may be one limb lead and two MCLs. An embodiment ofthe electrocardiogram measurement apparatus including the fourelectrodes according to the present invention is illustrated in FIG. 22. In FIG. 22 , the four electrodes 111, 112, 113, and 114 are providedon two plate-shaped wide surfaces, two on each wide surface.

The electrocardiogram measurement apparatus according to the presentinvention has been described in detail, but the present invention is notlimited thereto. The present invention may be changed in various formsaccording to the intention of the present invention.

An electrocardiogram measurement apparatus according to the presentinvention can be used as a portable electrocardiogram measurementapparatus that is convenient to carry and easy to use regardless of timeand place while it provides multi-channel electrocardiogram information.

The invention claimed is:
 1. An electrocardiogram measurement apparatus,comprising: a first electrode and a second electrode configured toreceive two electrocardiogram voltages of a body part in contacttherewith, respectively; two amplifiers configured to receive the twoelectrocardiogram voltages from the first electrode and the secondelectrode, respectively; one electrode driver configured to output adriving voltage; a third electrode configured to receive the output ofthe electrode driver and transmit the output of the electrode driver tothe body part in contact therewith; an AD converter connected to anoutput terminal of each of the two amplifiers to convert output signalsof the two amplifiers into two digital signals; a microcontrollerconfigured to receive the two digital signals of the AD converter; and acommunication means configured to transmit the two digital signals,wherein: the microcontroller is supplied with power from a battery; themicrocontroller controls the AD converter and the communication means;and the two amplifiers each receive and amplify one electrocardiogramvoltage simultaneously.
 2. The electrocardiogram measurement apparatusof claim 1, wherein the two amplifiers are single-ended inputamplifiers.
 3. The electrocardiogram measurement apparatus of claim 1,wherein one of the two amplifiers is a differential amplifier and theother one is a single-ended input amplifier.
 4. The electrocardiogrammeasurement apparatus of claim 1, wherein the electrode driver is a bandpass filter having a resonance frequency equal to a frequency of anexternal power line.
 5. The electrocardiogram measurement apparatus ofclaim 1, wherein the electrode driver is a constant voltage generator.6. The electrocardiogram measurement apparatus of claim 1, wherein theelectrocardiogram measurement apparatus is plate-shaped, wherein firstand second electrodes of the three electrodes are arranged spaced apartfrom each other by a predetermined distance in a longitudinal directionon one surface of a case of the electrocardiogram measurement apparatusso as to be brought into contact with both hands of a user by the user,and a third electrode is arranged on an opposite surface of the case. 7.The electrocardiogram measurement apparatus of claim 1, wherein the twoelectrocardiogram voltages are two limb lead signals, wherein four limblead signals are additionally obtained using the two limb lead signals.8. The electrocardiogram measurement apparatus of claim 1, wherein thetwo electrocardiogram signals are one limb lead and one MCL.
 9. Theelectrocardiogram measurement apparatus of claim 1, further comprising:a blood property measurement unit configured to measure blood properties(one or more of blood glucose level, ketone level, or INR).
 10. Theelectrocardiogram measurement apparatus of claim 1, further comprising:a body temperature measurement unit configured to measure a bodytemperature.
 11. The electrocardiogram measurement apparatus of claim 1,further comprising: a current detector configured to cause minutecurrent to flow when a plurality of electrodes is brought into contactwith a human body and to generate an output by detecting the minutecurrent.
 12. The electrocardiogram measurement apparatus of claim 1,wherein the communication means supports Bluetooth low energy (BLE). 13.The electrocardiogram measurement apparatus of claim 1, wherein theelectrocardiogram measurement apparatus and the three electrodes areinstalled on a watch or watch band, wherein one of the three electrodesis installed on an outer surface (surface not contacting the wrist) of aportion of the band, the portion being located on an inside of a wrist(a palm side, not a back side of a corresponding hand).
 14. Theelectrocardiogram measurement apparatus of claim 1, wherein theelectrocardiogram measurement apparatus and the three electrodes areinstalled on a ring worn on a finger, wherein one of the threeelectrodes contacts the ring wearing finger, and the other twoelectrodes are installed on an outer portion not in contact with thefinger, and wherein the two electrodes are arranged spaced apart fromeach other.
 15. The electrocardiogram measurement apparatus of claim 1,wherein the electrocardiogram measurement apparatus is attached to pantsby one or two clips serving as one or two electrodes.
 16. Theelectrocardiogram measurement apparatus of claim 1, wherein theelectrocardiogram measurement apparatus is attached to a watch band byone or two clips or slide guides serving as one or two electrodes. 17.An electrocardiogram measurement apparatus, comprising: a firstelectrode, a second electrode and a third electrode configured toreceive three electrocardiogram voltages of a body part in contacttherewith, respectively; three amplifiers configured to receive thethree electrocardiogram voltages from the first electrode, the secondelectrode, and the third electrode, respectively; an electrode driverconfigured to output a driving voltage; a fourth electrode configured toreceive the output of the electrode driver and transmit the output ofthe electrode driver to the body part in contact therewith; an ADconverter connected to an output terminal of each of the threeamplifiers to convert output signals of the three amplifiers into threedigital signals; a microcontroller configured to receive the threedigital signals of the AD converter; and a communication meansconfigured to transmit the three digital signals, wherein: themicrocontroller is supplied with power from a battery; themicrocontroller controls the AD converter and the communication means;and the three amplifiers each receive and amplify one electrocardiogramvoltage simultaneously.